Means for regulating electric motors.



No. 654,55|. Patented July 24, 1900.

- n. LUNDELL.

MEANS EOR REGULATING ELECTRIC MOTORS.

(Application filed Kay 19,, 1900.)

(No Model.)

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canoe "430i W UNITED STATES PATENT Grricn,

ROBERT LUNDELL, OF NEW YORK, Y.

'MEANS FOR REGULATING ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 654,551, dated July 24,1900.

Application filed May 19, 1900 Serial No. 17,264, (No model.)

To all whom it may concern: I

Be it known that I, ROBERT LUNDELL,a citizen of the United States,residing at New York, borough of Manhattan, in the county of New Yorkand State of New York, have made a new and useful Invention in Means forRegulating Electric Motors, of which the following is a specification.

My invention is directed particularly to the regulation of electricmotors of the series-parallel type and is designed to accomplish thesame results as are attained in the practice of the methods and by theuse of the means'described and claimed in a prior patent, No. 626,178,granted to me on the 30th day of May, 1899, and also to accomplishadditional results of importance, as will be hereinafter dis closed, theessentially-novel points of the invention being particularly pointed outin the claims at the end of this specification.

The invention has for its objects, first, to devise means forcontrolling series-parallel motors by varying the field strength and bycoupling the armature-circuits in series-parallel combinationsin themanner hereinafter described; second, to provide means whereby allexternal resistance in series with the armature circuits can bedispensed with, particularly when the current changes from series toparallel are being effected; third, to so arrange the field andarmature-circuits that for the lower speed combinations the motors mayautomatically return current to the line and at the same time act asbrakes, making mechanical braking unnecessary, except for minimumspeeds; fourth, to eliminate sparking at the brushes; fifth, to reducethe apparatus to a simple commercial form and at the same time increaseits efficiency to a higher degree than was possible with the meansdisclosed in my prior patent; sixth, to reduce the sparking at thecontroller-contacts to a minimum, and, seventh, to make the motorscapable of running at a great variety of fixed speeds, which speeds canbe materially varied without rewinding the motors.

As stated in my prior patent, it is customary to employ resistances inthe armaturecircuits of motors which are coupled in seriesparallelcombinations for the purpose of avoiding toosudden variations in speed,sparking at the brushes, and excessive flash ing at thecontroller-contacts. These resistances are particularly necessary whilethe change from series to parallel is being effected. There are,however, serious objections to all armature-resistances, the chiefobjections being loss of efficiency and unevendrops of voltage betweenthe resistance-terminals due to variations in the'load. In fact theresistances are only correct for one particular load upon the motors, asa light load will cause too small a drop of voltage in the resistanceitself and a heavy load will cause a greater drop of voltage than isrequired for correct variations in speed.

For a clear understanding of the invention, such as will enable othersskilled in the art to construct and use the same, reference is had tothe accompanying drawing, which is a diagrammatic view illustrating twoor more series-parallel motors and the application of my invention foreffecting the regulation thereof.

A and A represent the two armatures in a small motor-generator, thecapacity of which approximates seventy-five per cent. of the maximumwatt losses in the field-windings of all the motors which are to becoupled in series parallel. F and F are the respective shunt-fieldwindings of said motor-generator. B is a starting-box for themotor-generator, connected in a well-known manner to two current-mains Mand M, which I will suppose are connected to a largefive-hundred-voltpower generator. (Not shown.)

A A A and A represent armature-circuits of four motors with single-woundarmatures or two motors each with a double-wound armature, it beingimmaterial which case is assumed. However, thesearmature-circuits belongto the motors, the speed of which is to be governed. F represents all ofthe series field-windings of these various motors,which windings I willassume are all coupled permanently in series, the two ends beingconnected as shown on the drawing.

Numbers 1 to 12, 850., represent stationary controller-contacts,contacts 1 to 4, inclusive, belonging to the reversing-switch RS, andthe others 5 to 12, &c., belonging to the main rotary switch.

T to T represent the movable contacts on the main switch and on thereversing-switch,

said contacts being shown in plan development. They are supposed to bemounted on a cylindrical controller-cylinder in the usual way. Likeletters denote contacts which are or can be connected togetherelectrically.

R is a small resistance of large current capacity, which is usuallyshort-circuited, as shown, and R R are field-regulating resistances forthe generator side of the motor-generator, which are cut in or out ofcircuit by the main (controller) switch, as shown in the drawings.

'20 20' to w are conductors to which reference will be made inexplaining the mode of operation.

The dotted lines a a to 7t 71 indicate the various steps or notches onthe main (controller) switch or the positions thereof.

It will be noted on inspection of the drawing that thearmature-terminals (or brushes) on the generator side of themotor-generator are connected by conductors 10 w '10 to the two contacts1 and 4, which in turn may be connected through the movable contacts inthe reversing-switch RS to the terminals 2 and 3 of the field-windings FConductor 20 is also connected through conductor '11 to the positivemain M and the polarity of the motor-generator is so arranged whenrunning that the armature-terminal connected to conductor "m willlikewise be positive. The armature A of the motor-generator should be sowound that when its field-magnet F is fully charged the voltage andampere capacity of the armature should be sufficient to give the normalexcitation to the various fieldwindings represented by F. For example,if the total resistance of all the field-coils in series is one-half ohmand the current, required for normal or full excitation of F is sixtyamperes it follows that the electromotive force of A should be thirtyvolts with full field. It will of course be understood that if thefield-magnet F is weakened to such an extent (by the field-resistancesIt and R that the voltage at the armature-terminals of A is reduced toone-half it follows that the excitation of the field-windings F willalso be only one-half of the normalsin otherwords, the rate ofexcitation of F will vary according to the voltage of A This will evenbe true when current is flowing from the main M through conductor w andfield-coils F the, and through the armaturewindings A A A and A to thenegative main M, provided, however, that the internal ohmic resistanceof armature A is small or negligible as compared with the ohmicresistance of F I11 other words, the fieldwindings F will receive theirexcitation almost as if they were separately excited, which (being true)makes the various speeds as governed by the position of the controllernearly independent of the load. In order to make the speeds lessindependent of the load, it is only necessary to increase the ohmicresistance in the circuit leadin g from armature A by adding anauxiliary resistance It, which can be adjusted to suit existingconditions.

Referring now to the various armature-circuits A A" A A of the mainmotors, which are connected to the stationary contacts on the mainswitch in the simple manner shown, it will be noticed that the uppercontact 5 is connected by conductor 20 to an armatureterminal of A andto the previously-mentioned conductor 20, the lower contact 12 beingconnected to the negative main by conductor 10 It will thus beevidentthat before any current from the positive main M can pass through themain armature-circuits it must first pass through the field-windings Fand through armature A if the counter electromotive force of the latteris low.

Supposing now that the reversing-switch BS is closed, so that contacts Tand T establish connection from 1 to 2 and from 3 to 4, respectively,and that the motor-generator is running, we are then ready to observethe operation of the entire apparatus as the main switch is moved to thefirst position, (indicated by line a (0,) and so on until the lastposition, (indicated by line (L h.) The first position a a (first speed)connects all four armature-circuits A A A and A in series and thefield-magnet F of the motor-generator is given its highest excitation byreason of the two resistances It and B being cut out. In this position(first speed) the current flowing from the positive main M is small andthe armature A is supplying the principal portion of the strong currentsfor the field-windings F The second position Z) Z) (second speed) leavesthe main armaturecircuits in series, as before; but the field strengthof F has been reduced by a suitable resistance R, which in turn hasreduced the electromotive force of A and the current flowing throughfield windings F by an amount sufficient to give the desired increase inspeed. Third position 0 0 (third speed) further weakens thefield-windings and further increases the speed in the manner justdescribed. This has been accomplished by cutting in the resistance Rwhich is so adjusted that the speed becomes sufficiently near to thespeed which corresponds to the next position cl (1, (fourth speed.) Thispo sition d d has coupled the armature-circuits A A A A in seriesparallel, as will be found by following the connections, and the fieldsF and F have again been fully charged by reason of the resistances R andB being short-circuited. In this position there is of course morecurrent flowing from the main M through the arlnatures A", A, A and A"than when the same were all in series. Owing to the strength of thiscurrent the armature A will not be required to furnish as much currentto the field-windings F as in the first position of the main switch.Fifth position 8 e (fifth speed) and sixth position ff (sixth speed)leave the armature connections as in fourth position (Z (Z, but thefield-currents through F and F have been reduced, as described before,and the speed of the motors has been correspondingly increased. Seventhposition g g (seventh speed) couples all of the armatures A A A and A inparallel, and the current flowing from the main M is now greater thanever; in fact, strong enough to give to the field-windings F more thanis needed for full excitation, causing a rise of potential betweenbinding-posts 1 and 4, which in turn causes the armatureA to take part(the surplus) of the current. Eighth position h h (eighth speed)increases the speed by allowing a still greater part of the current fromthe main M to flow through the armature A It is not considered advisableto further weaken the field-windings F on account of possible sparkingatthe brushes in this last combination of armature-circuits when there isfull electromotive force for each armature. I have assumed all this timethat the counter electromotive force of A has kept the current flowingthrough F at strictly-determined rates dependent only on the fieldstrength of F and it follows, of course, that should the controller bemoved from the position of highest speed to any of the lower speeds animmediate reduction of speed must follow. Should the inertia of therevolving armatures and of the apparatus they are driving cause thespeed to be considerably higher than the correct speed for a givenposition of the controller, the armatures will then act as generators,driving current back into the mains and causing the same effect as ifmechanical brakes were temporarily applied. The smaller the ohmicresistances of the armatures A, A A A A and Aare, the more exact is anyspeed as determined by the position of the controller. Should it beadvisable, for instance, in a certain class of railway-work to slightlyalter this characteristic of the motors, so as to cause them to actafter the manner of ordinaryseries-wound motors, this can be done bysimply cutting in the small resistance R. Should it be necessary to makea permanent change in speedfor exam ple,if higher speeds should bedeemed advisable-this can be accomplished by increasing the resistancesR and R and by adding a permanent resistance in the circuit representedby conductor of.

I do not limit my invention to the specific arrangement of circuits andcircuit connections and apparatus hereinbefore described,

and illustrated in the accompanying drawing, for eitecting theregulation of one or more series-parallel electric motors when combinedwith a motor-generator and for effecting all of the results hereinbeforereferred to, as I believe it is broadly new with me to so combine suchan apparatus, and my claims are to be construed as of the most genericnature.

Having thus described my invention, what I claim, and desire to secureby Letters Patent of the United States, is-

1. The combination of a pair of currentmains' of constant electromotiveforce, one or more motors having armature-circuits capable of beingcoupled in series parallel; a source of variable electromotive forceadapted to vary the field strength and speed of said motor or motorsindependent of their armaturecurrents,with a controlling-switch havingcircuit connections between the current-mains, the motor or motors andthe source of variable electromotive force.

2. One or more motors having armature-cit cuits capable of beingconnected in series parallel; in combination with a source of variableelectromotive force connected in shunt across the field-windings of saidmotor or motors for the purposes described.

3. One or more motors having armature-circuits capable of beingconnectedin series par allel; in combination with a motor-generatorconnected to the field-windings of said motor or motors and adapted tovary the field strength thereof, independent of the armature-currents.

4. A motor-generator having its generatorarmature connected in shuntwith the fieldwindings of one or more motors; in combination with meansfor changing the electromotive force of the motor-generator for thepurpose of varying the field strength and speed of said motor or motors.

5. The combination of one or more seriesparallel motors with amotor-generator and one or more resistances for varying thecurrent-supply from the generator side of the motor=generator to themotor or motors.

In testimony whereof I have hereunto subscribed my name this 18th day ofMay, 1900.

ROBERT LUNDELL.

Witnesses:

C. J. KINTNER, M. F. KEATING.

